The purpose of the rollover detection system is activation of protection devices such as seat belts pretensioners, pop-up rollover bars or air bags, especially air bags protecting occupants during rollover accident.
There are number of ways for detecting rollover events. The most of the current systems use angular rate sensor (ARS) for calculating vehicle angle with respect to the horizontal plane. In such solutions, the algorithm numerically integrates the time dependent roll rate signal and provides the roll rate based angle as an output. As the ARS sensor signal always contains some errors (e.g. sensor drift, noise, etc.), these errors are accumulated during the integration process. As a result, the long term integration of ARS signal, without additional corrective mechanisms, can not be relied upon in determining the car inclination.
Known solutions, e.g. disclosed in U.S. Pat. No. 6,618,656, which are incorporated herein by reference, provide kinds of blending of the roll rate based angle with an accelerometer based angle. Nevertheless even in the case of using two independent accelerometers, during specific driving scenarios the averaged accelerometer based angle may contain errors.